1. Field of the Invention
This invention is directed toward apparatus and methods for gathering liquid samples using a submersible pump and subsequently preparing liquid samples for analysis, and more specifically directed toward the gathering and preparing of water samples for analysis for tritium content, where the samples are collected from underground formations penetrated by a borehole or collected at varying depths in surface ponds, canals and the like.
2. Background of the Art
The monitoring of liquid samples for contaminants is quite common in today's industrialized society. Such monitoring is carried out to track the efficiency of various manufacturing processes. In addition, such monitoring is employed to monitor potential hazards to humans and to the environment resulting from various manufacturing and processing operations.
Many types of nuclear manufacturing and processing facilities were built in significant numbers starting in the late 1940's and early 1950's. In the following decades, even more such facilities were built world wide as a result of the proliferation nuclear power, nuclear weaponry, and nuclear medicine. As with most manufacturing and processing operations, nuclear facilities generate wastes which can be hazardous to the environment and to the human and animal population, and such wastes must be monitored and disposed using methods which minimize health and environmental risks.
Attention is now directed toward nuclear facilities designed for the manufacture of nuclear weapons. More particularly, attention is directed toward "fission" weapon facilities used to produced weapons based upon induced neutron "chain" reactions in certain isotopes of uranium and plutonium. Great quantities of energy are released as a result of the induced chain reaction which is often referred to as an "atomic explosion". It is well known that one precursor for such an energy release or explosion is a "critical mass" of the fission material in order to sustain the chain reaction. Weapons designers also found in the 1940's that more efficient energy releases or explosion could be obtained if the chain reaction were initiated with a burst of neutrons from a device known in the art as a "trigger".
Several techniques have been used in nuclear weapons to construct triggers which produce large neutron fluxes for relatively short periods of time. The most common trigger is based upon the reaction EQU H.sup.2 +H.sup.3 =He.sup.4 +n
where
H.sup.2 =deuterium which is a hydrogen atom with a nucleus containing a neutron as well as a proton; PA1 H.sup.3 =tritium which is a hydrogen atom with a nucleus containing two neutrons as well as a proton; PA1 He.sup.4 =helium; and PA1 n=a neutron.
That is, when tritium is bombarded with deuterium at a sufficient energy, a nuclear reaction occurs which yields helium, plus a neutron with approximately 14 million electron volts (MeV) of energy. Triggers based upon this "deuterium-tritium" reaction therefore produce the neutron flux desired as a trigger for fission type weapons.
Tritium is used at fission type weapons manufacturing facilities and, as might be expected, most of these manufacturing facilities produce significant amounts of tritium. Tritium is radioactive with a half life of approximately 12.33 years, and decays to ground state He.sup.3 by the emission of a beta particle. Tritium reacts chemically as "normal" hydrogen (H.sup.1). It is well known that hydrogen is easily ingested by plant life and animal life including humans. Tritium is likewise easily ingested, but tritium ingestion results in the possible chemical binding of radioactive tritium within the plant or animal organism. As an example, tritium ingested by a human would result in radioactive tritium atoms being chemically bound or "lodged" within the human. Subsequently, as the tritium decays with a half life of 12.33 year, beta particles are emitted at the sites of the bound tritium causing significant biological and cellular damage in the area of emission. It is apparent, therefore, that waste liquid, such as water which is contaminated with tritium, can be a significant health threat to humans and to the environment. Such tritium contaminated water can be found in cooling ponds and drainage canals in the vicinity of nuclear facilities such as nuclear weapons plants. Furthermore, run-off water, which migrates and percolates into the earth around nuclear facilities, can also be contaminated with tritium. This becomes an especially critical problem if these contaminated waters migrate into drinking water aquifers. The result is a potable aquifer contaminated with a beta emitting tritium with a half life of 12.33 years.
Nuclear sites are currently monitored for tritium wastes. Liquid samples such as water are collected at varying depths from cooling ponds or canals. To monitor the migration of tritium contaminated water toward the water tables, test wells are often drilled about the site, ground water is allowed to flow into each of these wells, and water samples are taken at varying depths within the well. As an example, the detection of tritium contamination in a water sample gathered near the surface usually indicates that contaminated water has not migrated to deeper aquifers. Furthermore, the combination of tritium concentration measurements made at multiple depths in multiple wells can be used to generate a three dimensional map of any tritium contamination in the ground beneath the nuclear facility. Since nuclear facilities can be quite large and cover hundreds if not thousands of acres, it should be understood that tens or even hundreds of monitor wells are required to properly monitor water movement and possible ground water contamination.
Again examining current tritium monitoring techniques, liquid samples gathered from monitor wells, or at different depths within surface ponds or canals, must be pretreated prior to analysis for tritium. In one such pretreatment, the water is passed through a column containing a plurality of resin materials in order to remove certain cations and other materials which prohibit accurate tritium concentration measurements. This pretreatment can be performed at the sample site, but, using current technology, is preferably performed at a remote, analytical laboratory under controlled conditions. Tritium analysis is currently being performed at the remote, analytical laboratory. The time required to perform this type of analysis often takes one to two months from the time samples are received. The analysis cost per sample is also quite high. Considering that multiple sample sites such as monitor wells are needed, and that samples should be taken at varying depths at each sample site, the total cost of a monitor survey can be quite high. Furthermore, it is highly desirable to sample at a given site, such as a monitor well, as many as three to four times per day in order to detect early any tritium contamination so that remedial actions can be taken immediately. Although sampling at this time frequency can be done today, the current sample analysis turnaround of one to two months negates the usefulness of this method. Samples are obtained from wells of great depth.
One object of the present invention is to provide apparatus and methods for efficiently obtaining liquid samples at multiple sample sites and at multiple depths at each site. This is accomplished by a novel submersible pump system which can quickly be filled and which can quickly transfer sample to the surface from varying depth within the liquid. Sample liquid is acquired and transferred to the surface by means of valves cooperating with a surface compression and vacuum system. The sample collection pumps placed in deep wells are solenoid operated. This asssures measured and timed operation. The pumps, at any depth, deliver the desired quantity not withstanding length of tube. In fact, tubing volume is prevented from impacting sample size by timed valve operation.
Another object of the present invention is to provide apparatus and methods for efficiently treating, at the sample site, the samples obtained at great depths. This is accomplished by a valving system cooperating with a controller system such that the required sample is obtained, treated, and provided to an analyzing system upon command.
A further object of the invention is to provide apparatus and methods so that each sample site can be sampled at great depths three to four time per day, and that these samples can be pretreated prior to analysis.
Still another object of the present invention is to provide apparatus and methods for pretreating and analyzing a sample such that the concentration of tritium within the sample can be obtained, at the sample site, within thirty minutes after initiation of the pretreating and analysis steps.
A additional object of the invention is to provide apparatus and methods for gathering, pretreating, and analyzing water samples for tritium content completely under the control of a microprocessor controller and timer, and without human intervention.
There are other objects and applications of the present invention which will become apparent in the following disclosure.